There’s nothing big, fat or Greek about the play “Tiny Beautiful Things,” but Nia Vardalos is making it her own.

The Oscar-nominated screenwriter and star of “My Big Fat Greek Wedding” once again wears two hats. She stars in this Public Theater show, and adapted it for the stage from Cheryl Strayed’s bestselling memoir — a heart-wrenching and laugh-out-loud funny compilation of advice columns Strayed wrote for an online literary magazine. Vardalos plays Strayed, who also wrote “Wild,” as she supports, inspires and spars with various advice seekers posing prickly dilemmas (“I’m jealous of other people’s success, even if I like them” or “My two sons, 31 and 35, have returned to the nest. My home. They didn’t ask”).

The project seems tailor-made for Vardalos, who oozes a homespun warmth and empathy, the secret sauce that helped “Wedding” to become one of the highest grossing rom-coms of all time. A native of Winnipeg, the Greek Canadian has been married 24 years. Her 2013 memoir “Instant Mom” chronicles her adoption of a daughter.

You’ve written for yourself, in your own voice, but adapting someone else’s work is a whole other ballgame. How’d it feel?

I felt an incredible responsibility, as if someone handed me her baby on the subway.

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Well, that would certainly be sobering.

I’d encounter people, and mention “Tiny Beautiful Things,” and they’d say, “Oh, I loved that book!” So yes, I occasionally succumbed to the pressure, and found myself in a fetal position on the bathroom floor, saying, “I can’t do this,” or “You poser, what were you thinking?” But that’s the writer’s process. I think you’re supposed to hate it, then rip it apart before you love it. And that’s OK. Every aspect of climbing the mountain can be enjoyed. Just put on some hiking boots and get out there.

You sound just like Cheryl Strayed there.

I find such a kinship with her. As a writer, she’s remarkable — I wouldn’t put myself in her category. But . . . well, I feel there’s a reason why we met. She’s my friend now, and a colleague, and I just adore her.

What questions from the book struck a chord in your own life?

Whether I related to the subject of the letter or not, what moved me every time was the incredible bravery of the letter writers, and [Cheryl’s] unabashed kindness and compassion. She makes you want to have deeper, more honest, more authentic friendships than you’ve had before.

Was she prepared for you to change details here and there? That usually happens when adapting a work.

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Yes. I’m so grateful that, with the film adaptation of “Wild,” Reese Witherspoon and [director] Jean Marc Vallée treated her so well. If not, she might’ve closed the door on the rest of us Hollywood weirdos.

Strayed is incredibly open about her own life in her columns, more than most would be. What about you?

I’m more reserved.

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Yet you’ve written films from the heart. And there’s your memoir about adopting a little girl.

There are no limits to Cheryl’s intimate revelations. I protect a little bit. I admire Cheryl, but I’m not as direct in telling people what I need. I’m working on it. She makes you want to just . . . take off your clothes and walk down the street and go, “This is me.” [She laughs.]

Well, if you do that, nobody’s gonna hand you a baby on the subway.

HA! [She laughs loudly.] That’s hilarious. Oh, my God. [She imitates.] “Gimme your baby!” “No, lady, no. Hey, put on a bra.”

In the play, your character gets asked, “What advice would you give your younger self?” So, um . . . I’m askin’. What advice would you give?

That struck me. I’m a mom now, and constantly tell my daughter things that no one said to me. I look back at the me who I was — the theater geek who was not popular, the mutton-chopped Greek girl with glasses from my forehead down to my chin — just wondering how I’d ever get rid of all this facial hair and have an acting career. I’d love to go back and take that girl’s hand and say, “It gets better.” I saw this boy walking down the street recently dressed in a mix of two genders’ clothes . . . a masculine shirt, feminine pants, plus lipstick and open-toed shoes. I thought, “My GOD, what a wonderful time to be alive.” Wave your freak flag. We all need to go back to say to our younger selves, “There’s no one else like you. BE YOU.”